1. Field of the Invention
The present disclosure relates to an internal combustion engine and a water outlet structure of the internal combustion engine.
2. Discussion of the Background
For example, Japanese Unexamined Utility Model Registration Application Publication No. 4-006725 proposes a water outlet structure in which a thermostat is incorporated in a water outlet provided at a cooling-water outlet of a cylinder head in a water-cooled internal combustion engine. The thermostat selectively forms, from cooling water flowing into the water outlet through the cooling-water outlet of the cylinder head, a water flow that reaches a radiator and a water flow that directly reaches a water pump via a bypass passage.
In the proposed water outlet structure, the water outlet is attached to the cooling-water outlet provided at an end of the cylinder head in a cylinder arrangement direction, and the water outlet is provided integrally with a thermo case portion (thermo housing) of the thermostat.
The bypass passage projects perpendicularly to a cylindrical portion of the water outlet that extends perpendicularly to an end face of the cooling-water outlet of the cylinder head, and the thermo case portion is provided on an extension of the bypass passage.
The thermo case portion has an exit for the water pump, and a thermo cap (thermo cover) covering the thermo case portion has an entrance for cooling water flowing from the radiator.
An end portion of the cylindrical portion of the water outlet serves as an exit for the radiator.
In a cold state, the thermostat closes the entrance for cooling water from the radiator and opens the exit of the bypass passage. Hence, cooling water flowing from the cooling-water outlet of the cylinder head into the water outlet does not circulate through the radiator, but directly flows to the water pump via the bypass passage to promote a warm-up.
In a hot state, the thermostat opens the entrance for cooling water from the radiator and closes the exit of the bypass passage. Hence, cooling water flowing in the water outlet circulates through the radiator, is cooled by heat exchange, and is then supplied to the engine body to cool a cylinder block and the cylinder head.